U.S. patent number 6,118,253 [Application Number 09/304,414] was granted by the patent office on 2000-09-12 for charging and discharging control circuit and charging type power supply device.
This patent grant is currently assigned to Seiko Instruments Inc.. Invention is credited to Hiroshi Mukainakano, Koichi Yamazaki.
United States Patent |
6,118,253 |
Mukainakano , et
al. |
September 12, 2000 |
Charging and discharging control circuit and charging type power
supply device
Abstract
A charge/discharge control circuit has a voltage detecting
circuit for detecting at least one of an over-charge state, an
over-discharge state and an over-current state of a battery, a
control circuit for receiving an output signal of the detecting
circuit and outputting a signal for controlling the charging and
discharging of the battery, and an activating circuit connected to
the control circuit for selectively activating the control circuit
according to an output signal of the detecting circuit so as to
limit the power consumption of the charge/discharge control circuit
by operating the control circuit only when one of an over-charge
state, an over-discharge state and an over-current state of the
electric power source is detected.
Inventors: |
Mukainakano; Hiroshi (Chiba,
JP), Yamazaki; Koichi (Chiba, JP) |
Assignee: |
Seiko Instruments Inc.
(JP)
|
Family
ID: |
14864804 |
Appl.
No.: |
09/304,414 |
Filed: |
May 3, 1999 |
Foreign Application Priority Data
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|
|
|
|
May 6, 1998 [JP] |
|
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10-123607 |
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Current U.S.
Class: |
320/134;
320/136 |
Current CPC
Class: |
H02J
7/0063 (20130101); H02J 7/0031 (20130101); H02J
7/00 (20130101) |
Current International
Class: |
H02J
7/00 (20060101); H02J 007/00 () |
Field of
Search: |
;320/127,128,134,135,136
;429/61 ;340/635,636 |
References Cited
[Referenced By]
U.S. Patent Documents
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|
|
5547775 |
August 1996 |
Eguchi et al. |
5705913 |
January 1998 |
Takeuchi et al. |
5804944 |
September 1998 |
Alberkrack et al. |
5808446 |
September 1998 |
Eguchi |
5896025 |
April 1999 |
Yamaguchi et al. |
5959436 |
September 1999 |
Takashina et al. |
5959437 |
September 1999 |
Hamaguchi |
5990663 |
November 1999 |
Mukainakano |
|
Primary Examiner: Tso; Edward H.
Attorney, Agent or Firm: Adams & Wilks
Claims
What is claimed is:
1. A charging and discharging control circuit comprising: voltage
detecting means for detecting at least one of an over-charge state,
an over-discharge state, and an over-current state of an electric
power source; a control circuit for processing an output signal of
the voltage detecting means and outputting a signal for controlling
the charging and discharging of the electric power source; and a
current control switch circuit for supplying current to the control
circuit; wherein, for the purpose of decreasing current consumption
of the charging and discharging control circuit, the control
circuit is selectively operated by turning on/off the current
control switch circuit in response to an output signal of the
voltage detecting means.
2. A charging type power supply device comprising: a secondary
battery; a switch circuit connected to the secondary battery; an
external power supply terminal connected to the secondary battery
through the switch circuit; and a charging and discharging control
circuit for controlling the switch circuit; wherein the charging
and discharging control circuit comprises voltage detecting means
for detecting at least one of an over-charge state, an
over-discharge state, and an over-current state of the secondary
battery, a control circuit, and a current control switch circuit;
and wherein, for the purpose of decreasing current consumption of
the charging and discharging control circuit, the control circuit
is selectively operated by turning on/off the current control
switch circuit in response to an output signal of the voltage
detecting means.
3. A charging and discharging control circuit according to claim 1;
wherein the current control switch circuit is turned on to supply
current to the control circuit only when one of an over-charge, an
over-discharge and an over-current state of the electric power
source is detected by the voltage detecting means.
4. A charging and discharging control circuit according to claim 1;
wherein the electric power source comprises a secondary
battery.
5. A charging and discharging control circuit according to claim 4;
wherein the voltage detecting means comprises a comparator for
comparing a reference voltage with a voltage representing an output
voltage of the secondary battery.
6. A charging and discharging control circuit according to claim 5;
further comprising a voltage dividing circuit for dividing an
output voltage of the secondary battery and producing a divided
output voltage, the divided output voltage being supplied to the
comparator as the voltage representing an output voltage of the
secondary battery.
7. A charging and discharging control circuit according to claim 6;
wherein the voltage dividing circuit comprises one or more
resistors for dividing the output voltage of the secondary battery,
and wherein the reference voltage and the resistance value of the
resistors are selected so that an output of the comparator switches
when the secondary battery enters an over-charge state.
8. A charging and discharging control circuit according to claim 6;
wherein the voltage dividing circuit comprises one or more
resistors for dividing the output voltage of the secondary battery,
and wherein the reference voltage and the resistance value of the
resistors are selected so that an output of the comparator switches
when the secondary battery enters an over-discharge state.
9. A charging and discharging control circuit according to claim 5;
wherein the voltage detecting means further comprises a second
comparator for comparing a second reference voltage with a voltage
representing a current output of the secondary battery.
10. A charging and discharging control circuit according to claim
9; further comprising a resistor connected to an output of the
secondary battery, wherein the voltage across the resistor is the
voltage representing a current output of the secondary battery.
11. A charging and discharging control circuit according to claim
10; wherein the resistance value of the resistor and the second
reference voltage are selected so that an output of the second
comparator switches when the secondary battery enters an
over-current state.
12. A charging and discharging control circuit according to claim
1; wherein the voltage detecting means comprises a comparator for
comparing a reference voltage with a voltage representing an output
voltage of the electric power source.
13. A charging and discharging control circuit according to claim
12; wherein the reference voltage is an over-charge voltage of the
electric power source.
14. A charging and discharging control circuit according to claim
12; wherein the reference voltage is an over-discharge voltage of
the electric power source.
15. A charging and discharging control circuit according to claim
12; wherein the reference voltage is a voltage representing an
over-current state of the electric power source.
16. A charging and discharging control circuit according to claim
1; wherein the control circuit comprises a delay circuit for
delaying an output signal of the voltage detecting means so that
instantaneous and transient variations in output voltage of the
electric power source do not cause charging or discharging of the
electric power source to be stopped.
17. A charging and discharging control circuit according to claim
1; wherein the control circuit comprises one of a pull-up
transistor and a pull-down transistor for pulling up or pulling
down an output signal of the voltage detecting means to provide a
hysteresis effect.
18. A charging type power supply device according to claim 2;
wherein the current control switch circuit is turned on to supply
current to the control circuit only when one of an over-charge, an
over-discharge and an over-current state of the electric power
source is detected by the voltage detecting means.
19. A charging type power supply device according to claim 2;
wherein the electric power source comprises a secondary
battery.
20. A charging type power supply device according to claim 19;
wherein the voltage detecting means comprises a comparator for
comparing a reference voltage with a voltage representing an output
voltage of the secondary battery.
21. A charging type power supply device according to claim 20;
further comprising a voltage dividing circuit for dividing an
output voltage of the secondary battery and producing a divided
output voltage, the divided output voltage being supplied to the
comparator as the voltage representing an output voltage of the
secondary battery.
22. A charging type power supply device according to claim 21;
wherein the voltage dividing circuit comprises one or more
resistors for dividing the output voltage of the secondary battery,
and wherein the reference voltage and the resistance value of the
resistors are selected so that an output of the comparator switches
when the secondary battery enters an over-charge state.
23. A charging type power supply device according to claim 21;
wherein the voltage dividing circuit comprises one or more
resistors for dividing the output voltage of the secondary battery,
and wherein the reference voltage and the resistance value of the
resistors are selected so that an output of the comparator switches
when the secondary battery enters an over-discharge state.
24. A charging type power supply device according to claim 20;
wherein the voltage detecting means further comprises a second
comparator for comparing a second reference voltage with a voltage
representing a current output of the secondary battery.
25. A charging type power supply device according to claim 24;
further comprising a resistor connected to an output of the
secondary battery, wherein the voltage across the resistor is the
voltage representing a current output of the secondary battery.
26. A charging type power supply device according to claim 25;
wherein the resistance value of the resistor and the second
reference voltage are selected so that an output of the second
comparator switches when the secondary battery enters an
over-current state.
27. A charging type power supply device according to claim 2;
wherein the voltage detecting means comprises a comparator for
comparing a reference voltage with a voltage representing an output
voltage of the electric power source.
28. A charging type power supply device according to claim 27;
wherein the reference voltage is an over-charge voltage of the
electric power source.
29. A charging type power supply device according to claim 27;
wherein the reference voltage is an over-discharge voltage of the
electric power source.
30. A charging type power supply device according to claim 27
wherein the reference voltage is a voltage representing an
over-current state of the electric power source.
31. A type power supply device according to claim 2; wherein the
control circuit comprises a delay circuit for delaying an output
signal of the voltage detecting means so that instantaneous and
transient variations in output voltage of the electric power source
do not cause charging or discharging of the electric power source
to be stopped.
32. A charging type power supply device according to claim 2;
wherein the control circuit comprises one of a pull-up transistor
and a pull-down transistor for pulling up or pulling down an output
signal of the voltage detecting means to provide a hysteresis
effect.
33. A charge/discharge control circuit comprising:
a detecting circuit for detecting at least one of an over-charge
state, an over-discharge state and an over-current state of an
electric power source;
a control circuit for receiving an output signal of the detecting
circuit and for outputting a signal for controlling the charging
and discharging of the electric power source; and
an activating circuit connected to the control circuit for
selectively activating the control circuit according to an output
signal of the detecting circuit so as to limit the power
consumption of the charge/discharge control circuit by operating
the control circuit only when one of an over-charge state, an
over-discharge state and an over-current state of the electric
power source is detected.
34. A charge/discharge control circuit according to claim 33;
wherein the detecting circuit comprises a voltage dividing circuit
for dividing an output voltage of the electric power source and
producing a plurality of divided output voltages, an over-charge
voltage detection circuit, and an over-discharge voltage detection
circuit for detecting a level of selected ones of the divided
output voltages of the voltage dividing circuit, and wherein the
control circuit is receptive of output signals of the over-charge
voltage detection circuit and the over-discharge detection circuit
and outputs a signal for controlling the charging and discharging
of the electric power source based on output signals thereof.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a charging and discharging control
circuit for controlling the charging and discharging of a secondary
battery by turning on/off a switch circuit and to a charging type
power supply device of a secondary battery having the charging and
discharging control circuit incorporated therein.
As a conventional charging type power supply device comprising a
secondary battery, a power supply device shown in a circuit block
diagram of FIG. 2 is known. Such a structure is disclosed in, for
example, Japanese unexamined patent application publication No.
H4-75430 (1992) entitled "CHARGING TYPE POWER SUPPLY DEVICE." More
specifically, a secondary battery 101 is connected to an external
terminal -V0 or +V0 through a switch circuit 103. Further, a
charging and discharging control circuit 102 is connected in
parallel to the secondary battery 101. The charging and discharging
control circuit 102 has a function of detecting the voltage of the
secondary battery 101. In case the secondary battery 101 is either
in an over-charge state (a state where the battery voltage is above
a predetermined value--hereinafter referred to as an over-charge
protection state) or in an over-discharge state (a state where the
battery voltage is below a predetermined value--hereinafter
referred to as an over-discharge protection state), a signal is
output by the charging and discharging control circuit 102 to turn
off the switch circuit 103. Further, it is possible to restrict the
current through the switch circuit 103 by controlling the switch
circuit 103 so that, when the external terminal +V0 reaches a
certain voltage, the switch circuit 103 turned off to stop the
discharging. In other words, the discharging can be stopped when
the current is excessive (over-current control). This state is
hereinafter referred to as an over-current protection state. It is
the role of the charging and discharging control circuit 102 to
protect the battery against these states.
As another example of a conventional charging type power supply
device comprising a secondary battery, a power supply device shown
in a circuit block diagram of FIG. 3 is also known. The circuit
shown in FIG. 3 differs from that shown in FIG. 2 in that the
switch circuit 103 is connected in series with a negative electrode
111 of the secondary battery 101. In this way, the switch circuit
103 can function similarly in either case.
SUMMARY OF THE INVENTION
However, a charging and discharging control circuit structured in
the foregoing manner has a problem in that the current consumption
of the circuit itself shortens the operating time per charge of an
apparatus using the secondary battery.
FIG. 4 shows an example of an internal circuit of the charging and
discharging control circuit 102. In this circuit, only a circuit
for over-charge detection is shown. The charging and discharging
control circuit 102 comprises a reference voltage circuit 116 for
supplying a predetermined reference voltage Vr to an input terminal
of an over-charge detection comparator 119, a voltage division
circuit 120 including resistors R0-R1 for dividing the terminal
voltage of the secondary battery 101, and an internal control
circuit 124. Actually, the switch 103 is turned off not only in the
over-charge protection state but also in the over-discharge
protection state and in the over-current protection state.
The internal control circuit 124 has, for example, a function of
delaying a signal that is not from the detection circuit. Such a
signal is an external noise, and this is done to prevent the switch
circuit 103 from being turned on/off in case the battery voltage
varies instantaneously. Instantaneous turning on/off is a problem
because it stops power supply to the apparatus.
The internal control circuit 124 may also function as an
oscillator. This is because, depending on the circuit structure, a
clock is required to operate the delay circuit.
As described above, the internal control circuit 124 is formed of
several elements, and since it is normally operating, current
always has to be consumed.
The internal control circuit 124 mentioned above has to operate
only when the battery voltage is changed into a voltage to be
detected. However, since the internal control circuit operates and
the current is consumed even in case the state of the battery does
not vary at all, there is a disadvantage in that the operating time
per charge of an apparatus using the secondary battery is
shortened, which is shown in FIG. 7. The horizontal axis denotes
the time and the vertical axis denotes the current consumption of
the charging and discharging control circuit. Independently of the
state of the output of the over-charge detection comparator 119,
the current consumption of the charging and discharging control
circuit 124 is constant. Further, in a circuit where a clock is
required, the oscillator operates even when, essentially, it is not
necessary. This shortens the product life of the internal control
circuit, which has an adverse effect on the long-term reliability
of the charging and discharging control circuit.
An object of the present invention is, in order to solve these
conventional problems, by structuring a charging and discharging
control circuit such that an internal control circuit and the like
operate only when the voltage of a secondary battery reaches a
certain set voltage, to decrease the current consumption of the
charging and discharging control circuit, to extend the operating
time per charge of an apparatus using the secondary battery, and to
improve the reliability of the charging and discharging control
circuit. More specifically, the charging and discharging control
circuit is structured such that the internal control circuit begins
to operate when the certain set voltage is reached, and otherwise,
the internal control circuit does not consume the current from the
battery.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an explanatory view illustrating a circuit block diagram
of a charging type power supply device according to the present
invention.
FIG. 2 is an explanatory view illustrating a block diagram of a
conventional charging type power supply device.
FIG. 3 is an explanatory view illustrating a block diagram of
another example of a conventional charging type power supply
device.
FIG. 4 is an explanatory view illustrating a circuit block diagram
of the conventional charging type power supply device.
FIG. 5 is an explanatory view illustrating a circuit block diagram
of another embodiment of a charging type power supply device
according to the present invention.
FIG. 6 is a diagram illustrating a variation in the state of the
charging and discharging control circuit according to the present
invention.
FIG. 7 is a diagram illustrating a variation in the state of the
conventional charging type power supply device.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a block diagram of a charging type power supply device
comprising a charging and discharging control circuit of the
present invention. An embodiment of the present invention is
described in the following based on FIG. 1. A positive electrode
110 of a secondary battery 101 is connected to an external power
supply terminal +V0 through a switch circuit 103. In the embodiment
shown in FIG. 1, the switch circuit 103 is provided on the side of
the secondary battery 101 for charging and discharging control. The
voltage of the secondary battery 101 is detected by the charging
and discharging control circuit 102. According to the result of the
detection, the switch circuit 103 is controlled to be turned
on/off. The charging and discharging control circuit 102 comprises
a reference voltage circuit 116 for supplying a predetermined
reference voltage Vr to an input terminal of an over-charge
detection comparator 119, a voltage division circuit 120 including
resistors R0 and R1 for dividing the terminal voltage of the
secondary battery 101, a current control switch 140 and an internal
control circuit 124.
The output of the internal control circuit 124 is connected to a
terminal 125. The switch circuit 103 is controlled by the output of
the charging and discharging control circuit 102. The switch
circuit 103 is connected to the terminal 125 through a signal line
107.
An on/off control signal is sent to the switch circuit 103 from the
internal control circuit 124. A charger 108 for charging the
secondary battery 101 and a load 109 for which the secondary
battery 101 supplies current are connected between external power
supply terminals +V0 and -V0.
The over-charge detection comparator 119 has a function of
comparing with the reference voltage Vr of the reference voltage
circuit 116 the divided voltage output which is across the combined
resistance of the resistances R0 and R1 of the voltage division
circuit 120 and which represents the terminal voltage of the
secondary battery 101 to detect an over-charge state.
The output of the over-charge detection comparator 119 becomes high
when the level of the divided output voltage input to the + input
terminal of the over-charge detection comparator 119 becomes higher
than the reference voltage Vr. The internal control circuit 124 is
connected to the output of the over-charge detection comparator
119. The internal control circuit 124 has on output which is varied
from low to high with a predetermined time delay when the output of
the over-charge detection comparator 119 varies from low to high.
This is equivalent to provision of a delay circuit at the output of
the over-charge detection comparator 119, and thus, the charging
does not stop each time transient high voltage is applied. Only
when the battery voltage is kept high for a predetermined time or
longer, the switch circuit 103 is turned off to stop charging the
secondary battery 101. A capacitor 134 may be connected as shown in
FIG. 1 to extend the delay time. Further, the internal control
circuit 124 may be provided with various functions such as that of
an oscillator in addition to the delaying function.
A current control switch circuit 140 is turned on when the output
of the over-charge detection comparator 119 becomes high, in other
words, when an over-charge state of the secondary battery is
detected, to supply power to the internal control circuit 124. That
is, the on/off of the internal control circuit 124 is controlled in
response to the output of the over-charge detection comparator 119,
and no current is consumed by the internal control circuit 124
during an off period. In this way, since only the over-charge
detection comparator 119 operates when the terminal voltage of the
secondary battery 101 is normally below an over-charge detection
level, the current is made smaller, which is shown in FIG. 6. The
horizontal axis denotes the time and the vertical axis denotes the
current consumption of the charging and discharging control
circuit. The current consumption of the charging and discharging
control circuit varies around the time when the output of the
over-charge detection comparator 119 varies.
An embodiment shown in FIG. 5 illustrates a charging type power
supply device comprising a charging and discharging control circuit
that has functions of detecting over-charge, over-discharge, and
over-current of a battery. Two FETs (Field Effect Transistors) are
used as a switch circuit 103. An FET 112 for controlling
over-discharge and over-current is provided on the side of a
secondary battery 101, and an FET 113 for controlling over-charge
is provided on the side of an external power supply terminal -V0.
In this way, two FETs may form the switch circuit 103. The voltage
of the secondary battery 101 is detected by the charging and
discharging control circuit 102, and, according to the result of
the detection, the FETs 112 and 113 are controlled to be turned
on/off. The charging and discharging control circuit 102 comprises
a reference voltage circuit 116 for providing a predetermined
reference voltage Vr to - (minus) input terminals of an over-charge
detection comparator 119, an over-discharge detection comparator
118, and an over-current detection comparator 117, respectively, a
voltage division circuit 120 including resistors R1-R3 for dividing
the terminal voltage of the secondary battery 101, another voltage
division circuit 121 including resistors R4-R6 for dividing the
terminal voltage of the secondary battery 101, an internal control
circuit 124, and a current control switch 126.
In the embodiment shown in FIG. 5, the current control switch 126
is turned on when a high level signal is output from any one of the
over-charge detection comparator 119, the over-discharge detection
comparator 118, and the over-current detection comparator 117, that
is, when over-charge, over-discharge, or over-current of the
secondary battery is detected. This brings about an effect that the
current consumption is small if the comparators do not output a
high level signal. In other words, it is possible to lower the
current consumption even if plural detection level are
required.
In the embodiment shown in FIG. 5, using a combined circuit of
voltage division circuits 120 and 121 and FETs 122 and 123, the
operation of the over-charge detection comparator 119, the
over-discharge detection comparator 118, and the over-current
detection comparator 117 is adapted to have a hysteresis effect.
However, this is merely an example and it is not intended to limit
thereto the structure of the present invention. It is apparent that
the hysteresis operation may be implementetd by any other known
circuit structure capable of providing the same effect.
In the embodiments shown in FIGS. 1 and 5, examples of structures
having only one secondary battery 101 is controlled to be charged
and discharged are described. However, the present invention is not
limited only to the case where only one secondary battery is
controlled to be charged and discharged, but is similarly
applicable to a case where a plurality of serially-connected or
parallel-connected secondary batteries are controlled to be charged
and discharged.
In the present embodiments, the charging and discharging control
circuit is formed of a C-MOS (Complementary Metal Oxide
Semiconductor) circuit. However, it may be formed of any devices
such as bipolar transistors, and is easily implemented.
As described above, according to the present invention, by merely
adding a simple circuit, the current consumption is decreased when
the voltage of a secondary battery does not reach a certain set
voltage. Since the current consumption of the secondary battery is
suppressed, the life of the apparatus as a whole is extended and
the reliability of the charging and discharging control circuit is
improved.
* * * * *